The present invention relates generally to channel allocation in a frame-formatted, time-division, communication system, such as a radio LAN (local area network) operable to the proposed HYPERLAN/2 standard. More particularly, the present invention relates to apparatus, and an associated method, by which to allocate radio channels in a frame defined in the communication system. Allocations are made dynamically, e.g., on a frame-by-frame basis, responsive to determinations of anticipated need to communicate upon the random access channels during the frame.
A communication system is operable to communicate information between a sending station and a receiving station by way of communication channel. A radio communication system is a communication system in which the communication channel by which information is communicated between the sending and receiving stations is formed upon a portion of the electromagnetic spectrum. Such a communication channel is sometimes referred to as a radio channel. Because a radio channel does not require a wireline connection for its formation, a radio communication system inherently permits an increase in communication mobility relative to communication systems which require wired connections to form a communication channel.
Bandwidth limitations, which limit the communication capacity of many types of communication systems, are particularly limiting in many radio communication systems. Such bandwidth limitations in a radio communication system are typically due to limitations on the amount of the electromagnetic spectrum allocable to the radio communication system. Such bandwidth limitation limits the increase of communication capacity of a radio communication system. As a result, sometimes, the only manner by which to increase the communication capacity of the system is to increase the efficiency by which the allocated spectrum is utilized. Other types of communication systems similarly can exhibit a communication capacity increase as a result of increase in the efficiency by which the communication channels formed between sending and receiving stations of such systems are utilized.
Digital communication techniques, for instance, provide a manner by which to increase the efficiency by which to effectuate communications upon communication channels of a communication system. Implementation of digital communication techniques in a radio communication system is particularly advantageous due to the particular need to efficiently utilize the spectrum allocated to such a system.
Information which is to be communicated in a communication system which utilizes digital communication techniques is typically digitized into discrete, digital bits. Groups of the digital bits are sometimes formatted into packets, referred to as data packets. The data packets are communicated by the sending station, either individually or in groups, at discrete intervals to a receiving station. Once received at the receiving station, the packets of data are concatenated together to recreate the informational content contained therein.
Because packets of data can be communicated at discrete intervals, the communication channel upon which the packet is transmitted need not be dedicated to a single sending-receiving station pair. Instead, a shared communication channel can be used to communicate packets of data communicated between a plurality of sending-receiving station pairs. Because of the shared nature of the shared channel, improved communication capacity is possible.
Packet data communications are effectuated, for instance, in conventional LANs (local area networks). Wireless local area networks, operable in manners analogous to wired LANs, have also been developed and are utilized to communicate packets of data over a radio link. A HIgh PErformance Radio Local Area Network type 2 (HIPERLAN/2) standard promulgated by the ETSI BRAN (broadband radio access network) project sets forth a standard of operation of an exemplary wireless LAN. Mobile terminals operable therein transmit packet data upon a radio link to an access point of the infrastructure of the wireless LAN.
A frame structure is defined in the HIPERLAN-2 standard at a MAC (medium access control) layer defined therein. The MAC-frame includes four portions, a broadcast phase (BC), a downlink (DL) phase, an uplink (UL) phase, and a random access (RA) phase. Data communicated during the broadcast phase of the frame generally pertains to control information. The downlink and uplink phases carry user data and control data to, and from, a mobile terminal according to a reservation-based scheme. And, the random access phase permits random access by mobile terminals to random access channels defined therein. In contrast to the downlink and uplink phases, a reservation-based scheme is not utilized in the random access phase of the MAC-frame. The length of the MAC-frame is fixed to be of a 2 ms duration, but the length of each phase of the frame is selectable.
While communication of data upon a random access channel of the random access phase provides a simple manner by which to effectuate communication of data, lack of coordination between separate sending stations of separate sending-receiving station pairs might result in collisions of data if communicated concurrently upon the same random access channel. That is to say, separate sending stations might attempt to transmit separate packets of data during overlapping time periods. Typically, when a collision condition occurs, the packets of data interferes with one another to an extent to prevent the recreation of their informational content subsequent to reception at their respective receiving stations.
To reduce the likelihood of occurrence of collisions between packets of data transmitted upon the random access channels beneath a threshold, an adequate number of random access channels is required to be allocated to form a portion of the MAC-frame. By increasing the number of random access channels of which a MAC-frame is formed, the likelihood of a collision occurring upon any particular random access channel is reduced. However, by increasing the number of random access channels, the efficiency of channel utilization is reduced, particularly because the MAC-frame is of a fixed length.
Existing manners, and proposed manners, by which to select the number of random access channels to form a portion of a MAC-frame generally do not provide a quantitative manner by which to select the number of random access channels of which to form the random access portion of a MAC-frame. That is to say, presently, there generally is no manner by which to quantitatively balance the competing goals of minimizing the likelihood of the occurrence of a collision and the goal of maximizing communication capacity in the communication system.
A manner by which to allocate the number of random access channels to form a portion of a frame on a quantitative basis would therefore be advantageous.
It is in light of this background material related to communications in a frame-formatted communication system that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, by which to allocate random access channels in a frame-formatted communication system.
Quantitative determinations are made of anticipated communications upon random access channels during the frame. Determinations are made dynamically, such as on a frame-by-frame basis. When a determination is made of an increased need to communicate upon random access channels, increased numbers of random access channels are allocated to form a portion of the frame. And, conversely, if a determination is made that lessened numbers of random access channels are anticipated to be needed to effectuate communications, the frame is formed of lessened numbers of random access channels.
In one implementation, an embodiment of the present invention is operable to form a portion of wireless LAN (local area network), such as that set forth in the HIPERLAN/2 (high performance local area network/type 2) standard. In such a wireless LAN, a plurality of mobile terminals are operable to communicate by way of a wireless link with an access point when positioned within a coverage area defined by the access point. A typical wireless LAN also includes a plurality of access points, each defining a coverage area and between which communication handovers are effectuable as a mobile terminal travels between coverage areas defined by successive ones of the access points.
Frame-formatted communications are defined in the HIPERLAN/2, as well as other, standards. In particular, the HIPERLAN/2 standard defines a MAC (medium access control)-frame structure containing a variable number of random access channels. The random access channels provide random access to mobile terminals to send messages to the network infrastructure of the LAN to request the allocation of dedicated communication channels to effectuate communications thereon. Operation of an embodiment of the present invention determines how many random access channels are required to be needed during a frame to ensure that the likelihood of the occurrence of the collision upon a random access channel is less than a selected threshold.
In one aspect of the present invention, determinations are made as to the number of mobile terminals which are associated with an access point. These determinations are made, for instance, responsive to registration messages sent at selected intervals by mobile terminals. Registration messages are sent by the mobile terminals also during their initial powering-on. And, determination of the number of mobile terminals associated with an access point is also responsive to detection of indications of handovers of communications from another access point. Responsive to such determinations of the mobile terminals associated with an access point, selection is made of the number of random access channels to form a portion of a frame.
In another aspect of the present invention, determinations are made both of the number of mobile terminals associated with an access point but also of the number of such associated mobile terminals to which channel allocations have been reserved. A difference is formed between the number of mobile terminals associated with the access point and the number of mobile terminals which further already have a channel assignment allocated thereto. Selection of the number of random access channels to allocate to form a portion of the frame is made responsive to such difference. At least one random access channel is assigned to each frame even if all of the mobile terminals associated with the access point also have allocated thereto a channel allocation. Thereby, if a mobile terminal, previously unassociated with the access point, becomes associated with the access point during the time period of the frame, a random access channel is available thereto upon which to transmit a message thereon by the additional mobile terminal.
In another aspect of the present invention, determination is also made as to the communication-service type anticipated to be communicated during the frame. The communication-service type has associated therewith a priority level. Certain communication-service types are more time-sensitive than others. If the anticipated levels of communication of a communication-service type of a high priority level is small, the number of random access channels determined to be necessary is selected to be correspondingly large. If, conversely, the amount of communications of the communication-service type of a high priority level is relatively large, the number of random access channels should be fairly small. Selection of the number of random access channels of which to form a portion of the frame is made responsive thereto.
In another aspect of the present invention, the access point is further capable of selectably generating a wake-up indicator during the frame. A determination is made as to whether the access point is to generate a wake-up indicator during the frame. Selection of the number of random access channels of which to form a portion of the frame is made responsive to such determinations. If determination is made that the access point is to send a wake-up indicator during the frame, selection is made to increase the number of random access channels of which to form a portion of the frame.
Because quantitative determinations are made of anticipated communication conditions during the frame, allocation of the number of random access channels most appropriate to form a portion of the frame is better made. As a result, a better balance is able to be made between increasing the number of random access channels to minimize the likelihood of collision conditions thereupon, and most efficiently utilizing the communication capacity of the allocated spectrum to the communication system.
In these and other aspects, therefore, apparatus, and an associated method, is provided for selecting a selected number of random access channels of which to form a portion of a frame. The frame is defined in a multi-user communication system in which at least one sending station is capable of random access to a selected number of random access channels to Ocommunicate data to a receiving station. The selected number of random access channels form a portion of a frame of communication channels. A determiner is coupled to receive indications of a parameter indicative of anticipated communications between the at least one sending station and the receiving station. The determiner determines a number of random access channels needed to maintain a collision possibility of collisions between data communicated by the at least one sending station upon a random access channel of the frame beneath a threshold. A selector is operable responsive to determination made by the determiner. The selector selects how many random access channels are to form the portion of the frame.